Food Allergy or Food Intolerance: A HealthCentral Explainer

Food allergy is an overreaction of the immune system triggered by something you eat. The response can range from mild to severe, and in some cases, life-threatening, if anaphylaxis occurs. The allergic response typically takes place any time from within a few minutes to several hours after exposure to the allergen. Symptoms include itching and swelling in your mouth or throat, vomiting, diarrhea, abdominal cramps, hives or eczema, difficulty breathing and a drop in blood pressure.

The first time someone is exposed to a food allergen the immune system produces IgE antibodies to that allergen and they circulate through your blood and attach themselves to immune cells. The next time a person is exposed to that allergen, it binds to the IgE antibodies attached to the immune cells, and that signals a massive release of histamines and other chemicals.

Anaphylaxis is unpredictable and always a possibility when someone is exposed to a food allergen. It needs to be treated immediately, which is why carrying an auto-injector device with epinephrine is essential for anyone with food allergies. Another measure is a medical alert bracelet that lists your allergies. And even if a reaction appears to be mild, it’s a good idea to seek medical help. It’s very hard to know if mild symptoms will lead to anaphylaxis.

According to the CDC, children are at greater risk for food allergies if they have a family history of asthma and allergies, elevated allergen-specific IgE concentrations or if both parents have food allergies.

What is food intolerance?

Food intolerance can be very unpleasant, but doesn’t trigger the serious immune response that food allergies do. Intolerance can cause abdominal cramps, bloating, flatulence, malnutrition, abdominal distension, diarrhea, bad-smelling stool and other GI issues. However, once the food has passed through the small intestine, the symptoms go away and there is no inflammation or damage to the intestine. The most common are lactose intolerance, which occurs after consuming dairy products, and gluten intolerance, which occurs after eating foods containing wheat, rye, barley and oat.

Gluten intolerance is not to be confused with Celiac disease, which is gluten hypersensitivity. Celiac disease causes severe intestinal inflammation while gluten intolerance does not.

What is the difference between food allergy and intolerance?

The main difference between food allergy and food intolerance is that a food allergy triggers a response from your immune system while food intolerance irritates your digestive system. Intolerance does not carry the same risks as a food allergy, and symptoms go away after the irritating food has passed. However, it’s still a good idea to avoid food to which you’ve shown an intolerance so you don’t repeat that unpleasant experience.

What are examples of food intolerance and food allergy?

The most common food intolerances are lactose, gluten and food additives, such as MSG and sulfites. MSG is used to enhance taste and color, while sulfites are used to protect against the growth of microbes and increase crispness. Sulfites can also be naturally occurring in foods or be generated in wine during the wine-making process. All sulfites will be listed under the ingredients on food labels.

The most common food allergies include milk, soy, eggs, peanuts, tree nuts, wheat, fish and shellfish. Foods eaten on a regular basis increase the likelihood that a person will develop an allergy. For instance, the NIAID reports that rice allergies are more common in Japan than the United States, and codfish allergies are more common in Scandinavian countries than the United States.

Why is the difference important?

It’s important to be aware of your body’s reaction to food to determine if you are experiencing an allergy or intolerance. If you find your symptoms align with that of a food allergy, you need to seek immediate medical attention. It’s also important to talk to your doctor about a plan in the event of a severe allergic reaction. If you are experiencing food intolerance, make note of what you need to avoid and also which replacement products are available, such as gluten-free breads and pasta or lactose-free dairy products.

HealthCentral's team of editors based in Arlington, Virginia, collaborates with patient advocates, medical professionals, and health journalists worldwide to bring you medically vetted information and personal stories from people living with chronic conditions to help you navigate the best path forward with your health — no matter your starting point.